Carbothermic reduction kinetics of Ka’oje (Nigeria) manganese ore

The kinetics of carbothermic reduction of manganese ore from Ka’oje deposit has been established. X-Ray diffraction analysis of the as-mined ore samples affirmed the presence of pyrolusite as the major manganese mineral in the ore, existing alongside with iron mineral present as hematite optically identified by transmitted infrared light microscopy. Samples with particles size ranges—106 μm were isothermally treated using charcoal of 52.17% carbon content as the reductant. The treatment was carried out at 550˚C, 600˚C, 650˚C and 750˚C with varied roasting retention time. Ore-mineral reduction kinetic model equations were developed using the generated thermal data. Results showed that the apparent activation energy (Ea) of the chemical reaction controlled reduction was 19.99 KJ/mole using the diminishing area rate equation. Obtained Ea values for diffusion controlled reduction of the ore-minerals were 36.28 Kj/mole and 29.56 KJ/mole using Jander and Ginsthing-Brounshtein equations respectively. These hereby established reduction susceptibility of the manganese oxide mineral from higher oxide to lower oxides meant for further hydrometallurgical treatments

Electrolytic deposition of manganese dioxide from Nigerian manganese ore using graphite electrodes

Abstract: Super rich manganese dioxide got deposited at the anode when manganese sulphate solution was electrolytically decomposed, and the deposits called Electrolytic Manganese Dioxide (EMD). Manganese ore containing about 35.79% manganese from Ka’oje (Kebbi State, Nigeria) with pyrolusite (MnO2) as the major manganese mineral alongside iron mineral present as hematite, was the resource material. Some 1973.31g of beneficiated ore sample (75 to 600μm) was isothermally reduced with charcoal (52.17% carbon) at 6000C for one hour. The paramagnetic high oxide ore got reduced to a ferromagnetic lower oxide containing 38.90% manganese. Some 610g portions of the reduced ore were leached in varied concentrations of sulphuric acid (1.0M, 1.5M and 2.0M) at 500C for one hour and 42.36% leaching efficiency was achieved with 2.0M acid. Calculated elemental mass balance revealed that 2.0M acid dissolved 100.52g of manganese into the leach liquor as manganese sulphate along with 13.83g of iron and 7.47g of aluminium as the major elements. Each leach filtrate was purified with aqueous sodium hydroxide except some 600ml of filtrate from 2.0M acid leaching which was decomposed unpurified for comparison. The filtrates were respectively electrolyzed at 2.5V, 3.0V and 4.0V driving potentials for five hours using graphite electrodes. Analyses showed that the purified liquor extracted with 2.0M acid and electrolysed at 4.0V deposited the best quantity and quality of EMD, containing 98% MnO2. This high grade EMD is a principal precursor in Ferro-alloy production for steel making and also an important raw material for electrochemical cells and other allied manganese-based chemicals

Investigation of the potentials of Nigerian salt deposit as fluxing materials in secondary aluminium production

Secondary aluminium has been a major contributor to the total supply of aluminium to the national economy. To obtain high-grade secondary aluminum from scraps, melted scraps are subjected to such treatment as fluxing. Fluxing improves the quality of secondary aluminium products by eliminating the impurities and protecting the surface of the melt from contamination. In this work, fluxing of aluminium scrap was carried out using salt obtained from Keana in Nassarawa State. The preliminary investigation carried out on the salt indicate a high level composition of various cations and anions such as Na+, K+, Cl-, C03-, that are characteristic of aluminium fluxes. Various percentages by mass of Keana salt was used in fluxing melt obtained from aluminium scraps. The results of tests carried out on the specimen using cast samples indicate that the optimum fluxing proportion of this salt is 1.5wt.%. The corresponding values of mechanical properties are UTS = 141N/mm2, Percentage Elongation = 1.11; Brinnel Hardness = 50HRB; Impact strength = 51.54J. These values compares well with those obtained using standard Coverall fluxing materials and in some instances, samples fluxed with Keana salt gave better parameters. Keywords: Secondary Aluminium, Scraps, Fluxing, Salt, Mechanical Properties. [Global Jnl Engineering Res. Vol.2(1&2) 2003: 11-15

Characterisation of Natural Moulding Sands from Selected Deposits in Maiduguri-Nigeria for Casting Applications

Natural moulding sands consist of refractory sand grains associated with clay right from their deposit locations. In Maiduguri, there are some sand casting activities taking place. However, there seems to be no single graded source of moulding sand that the practitioners can use for producing qualitative sand castings. Therefore, this study was carried out to characterise moulding sands from five selected deposits in Maiduguri for possible use in sand casting applications. Chemical compositions of sand samples were determined using XRF Analyser while American Foundrymen’s Society (AFS) standard laboratory tests were used to determine the physico-mechanical properties. The results of the characterisation revealed the following ranges of values; clay content from 21.8% to 47.2% corresponding to Pompomari and Gwange/Fori, grain fineness number from 50.94 AFS to 95.02 AFS corresponding to Pompomari and Gwange/Fori deposits.. Other physico-mechanical properties determined included; green and dry compressive strengths, permeability, loss on ignition and refractoriness. Results of chemical composition analysis show SiO2 having dominance in all the samples (90.10 % to 66.77 %) with trace elements of CaO, Fe2O3, Al2O3, MgO, TiO2, K2O, NaO2 also present within acceptable limits. The overall results show that all deposits have potential for use in sand casting applications for the casting of nonferrous metals and malleable and ductile iron. However, the clay content range given above is a major problem compared with the standards recommended by the American Foundry Society. This did not only limit their uses to low melting point alloys because of relatively lower refractoriness values but also possesses danger to their life expectancy. In conclusion, the use of the deposits characterised especially the Gwange/Fori deposit with clay content of 47.2 % should be used with caution because of the possibility of developing gas defects like blowholes and pinholes. All the other four deposits have been recommended for full exploitation for use in sand casting applications for casting of nonferrous metals as well as malleable and ductile irons. Finally, on the basis of the overall properties, the five deposits have rated in the following order of preferences; Dala Lawanti, Pompomari, Gwange/Fori, Gamboru and University of Maiduguri respectively